It's probably true that on the average dairy farm in the old days you didn't need 3 phase, with most motors only being 1 hp, as my father didn't in his dairy, but now as you're finding out the modern dairy farm uses a lot more motors and the total current draw is getting quite near to the 100 amp capacity of a single phase supply, especially on start up.
As your sparky suggests, going to 3phase is quite a cost, and the main benefit for most farms is the ability to run big motors (my biggest is 35hp), so one of the questions for you is whether you want to do like vantage has done in his previous post and update part of your setup soon, like put a bigger bulk tank.
Of course you could avoid the huge cost of getting it installed by putting in a generator, although it seems like you could avoid most if they're upgrading the lines.
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